Transformer coil



June 22, 1948. M. TAMA 2. 3.

TRANSFORMER COIL Filed Sept. 29, 1945 3 Sheets-Sheet 1 I INVENTOR. III WAY/4 /AW AIW/AV/ MARIO TAMA u n an, Illlllllllllllll w w m w y n\\\\\\\\\\\\\\\\ ATTORNEY June 22, 1948.

Filed Sept. 29, 1945 M. TAMA 2,443,842

TRANSFORMER COIL 3 Sheets-Sheet 2 J. I I 1 INVENTOR MARIO TAmA ATTORNEY June 22, 1948. M. TAMA TRANSFORMER COIL Filed Sept. 29, 1945 s Sheets-Sheet s INVENTOR MARIO TA MA w wl bvv ATTORNEY 6 I, nw I A fi I I I I I I I I I I 7 II...IIIII|I III ll- 5 [I r 1 Patented June 22, 1948 TRANSFORMER COIL Mario Tama, Morrlsville, Pa., minor to Ajax Engineering Corporation, Trenton, N. J. I

Application September 29, 1945, Serial No. 619,317

The invention relates to a multilayer inductor coil, particularly for use in induction furnaces.

As generally known the inductor coils surrounding the core and forming the primary of the current transforming system are located in cooling ducts of the induction furnaces, and these cooling ducts are positioned within the secondary refractory blocks.

It is the main object of this invention to comply with certain specific requirements of the furnace operation with regard to these primary inductor coils and particularly with the operating conditions in the coil cooling ducts.

It is a further important object of the invention to provide a rigid inductor coil structure adapted to be easily handled and installed in the cooling ducts as a ready made unit.

It is another important object of the invention to produce an inductor coil construction that will withstand the severe stresses and operating temperatures of an induction furnace for longer periods and will not collapse even if the temperature rises unduly.

It is also an object of the invention to provide an inductor coil whose windings are so fixed in mutual position that no relative movement thereof will occur under any overload or raised temperature.

Itis an important object of the invention to produce an inductor coil where substantially the entire surface of the windings is exposed to the stream of the cooling medium.

It is another object of the invention to produce an inductor coil which can be handled, transported and used as a ready-made unit which is resistant to mechanical stresses.

It is also an object of the invention to provide an inductor coil of a shape which corresponds to the mounting space of the cooling duct of an induction furnace and which permits its easy and safe installation with a minimum of assembly costs and time.

3 Claims. (Cl. 175-356) In order that the adaptability and usefulness of the instant inductor coil for induction furnaces and particularly for those of the submerged resistor type for melting metals may be fully fabricating procedure the solution of an insulating coating substance is applied, for instance sprayed, on the coil as each layer is wound; after the winding is completed the solvent is removed and the coating material cured by heating.

In order to increase the mechanical strength and resistance of the coils resin impregnated paper and cloth tape strips are used to support and to space the windings; furthermore, blocks made of insulating materials, such as porcelain and glass, have been suggested as a means to stabilize the coil forming structure.

Spacer devices of various shape and construction have been devised to separate and to support the coil windings and to strengthen the same; radial spacers have been recommended to create ducts between the windings for the circulation of a cooling fluid; to further increase the stability of the coils spacing strips extending parallel to the longitudinal coil axis have been interlocked with radial spacers to hold the latter in place.

Another manner of makin induction coils resides in winding the same on a supporting tube of an insulating material, such as asbestos cement compositions; this manufacturing mode renders the coils very voluminous and seriously impairs the heat dissipation from the inner face; this situation becomes the more objectionable when high current densities are used.

Extensive investigations have proven that none of the hitherto known induction coil structures satisfactorily complies with the peculiar requirements of an induction furnace where most unusual sudden temperature or power variations are experienced due, for instance to failure of the cooling system, to partial leakage of the metallic charges and so forth.

The invention is particularly devised to attain a satisfactory working of the induction coil in cases of sudden irregularities of the furnace operation.

With the various above recited objects and purposes in view the invention comprises in its broad aspect a multilayer substantially rectangular induction coil having at least one air duct between the individual coil windings, which coil may be handled, transported and used as a rigid, mechanically resistant, ready made unit and may be as such installed and mounted without difficulty in the cooling duct of an induction furnace. A reinforcing skeleton consisting of arcuated longitudinal spacers extending along the inner faces of-the substantially right-angled corner portions and through the cooling duct of the coil is provided to impartto the coil a high degree of mechanlcal stability, dielectric strength and resistance to high temperature, thereby eliminating the danger of collapse.

An important characteristic of the invention is the use of non magnetic metal as a construction material for the reinforcement of the coil structure between the individual layers thereof.

The use of metals has been hitherto considered inadequate for the purposes here in question, because metals are conductors and vastl reduce the arc-over voltage between the coil layers.

Another objection to the use of metallic spacers resides in the possible induction of strong eddy currents in the structural elements of the coil, for instance in the spacers, especially if the latter are located in the portions of the coil where a strong alternating electromagnetic field prevails; such eddy currents would result in overheating of the metallic spacers.

The invention avoids the above recited dangers because the spacers even made of nonmagnetic metals are located at places where the electric fields are of moderate strength. 7

Additional important items and advantages of the. invention will be apparent from the following detailed description of a preferred embodiment which is illustrated in the attached drawinss.

In these drawings,

Fig. 1 is an end view of the finished coil,

Fig. 2 is a fragmentary side view seen in the direction of arrow A, and

Fig. 3 is another fragmentary side view seen in the direction of arrow B, both these figures showing the coil in the upright position, and

Fig. 4 is a sectional fragmentary elevation on line 44 of Fig. 1.

Referring to the drawings the induction coil illustrated therein has a substantially rectangular shape; it is composed of four layers l of flat copper wire; these four layers are divided into two the outer coiled windings; the purpose is to pre-' vent longitudinal displacement of the coil windings.

groups, two layers forming an inside and the other faces of the coil windings.

The rigidity of the coil is attained by the pro-. vision of two types of longitudinal members represented by four supporting strips I and four spacer strips 4.

The four supporting members I extend longi- -tudinally throughout the length of the coil and along the inner faces of its substantially rightangled corner portions; members I project at both ends over the coil windings as clearly apparent from F18. 3. i

The spacer strips I are arranged in a simil manner and in paralleled relationship to members 3; these spacers extend through air duct 2; they also project with their ends over the coil windings.

Supporting members I and spacer strips 4 are arcuated to substantially correspond to the curved shape of the corner portions of the coil and to snugly fit therein; they are, made of non-magnetic metallic materials, such as copper, bronze, austenitic steels.

The spacers 4 are embedded in an insulating wrapping I, such as glass-tape or cloth. The

It is to be noted that the non magnetic metallic supporting members I and spacer strips l are only used at the inside and between the coil windings where the electromagnetic alternating fields are comparatively low, but not at the outside of the windings, where the secondary circuit of the induction furnace is located.

The coil windings are, provided in the usual manner with two terminal leads I which with the exception of their end portions are covered in the usual manner with insulating tape I; a simiv lar insulation is applied to the windings.

The projecting bottom ends of strips I provide additional measures for stiffening the structure; for this purpose a bridging strip II, see Fig. 3, is interposed between and connected with these ends; bridge I I serves as a means for an expedient and reliable mounting of the coil on the transformer core which in turn is fastened tothe outer metal casing of the furnace; this bridging strip It may be replaced by other suitable means adapted to fasten the coil supporting structure to the core.

The invention also provides in conformity with its particular purposes a new manner of winding the coil,

Induction coils for use in modern high-capacity induction furnaces have a large size; for expeditious reasons a plurality of the thick wires are wound at the same time.' As indicated by the heavy lines II, Figs. 2 and 3, which mark the extent of the simultaneously wound fiat copper wires I, having a cross section of about V4 by V2 inch, five wires are manipulated simultaneously in accordance with the shown exempliflcation of the invention. The simultaneous winding procedure of the five wires l bears no dimculty when winding the length of each coil layer; but it is apparent that. the simultaneous transition of a group of five copper wires into the next adjacent coil layer will result in the creation of uneven coil ends.

A simple way of solving this problem has been found, forming an element of this invention, which will be explained in connection with the following description of manufacturing the coil.

For this purpose four supporting members I. are set in position on a. suitably shaped rectangular mandrel. not shown, which will be driven by a coil winding machine and which conforms to the inner hollow space of the coil; the first coil layer is produced on the supporting members I by winding a group of five wires I simultaneously.

Upon completion of the first coil layer the transition into the next adjacent layer is effected by directing the individual wires i of the group separately and successively into the same; this procedure is observed every time at the transition from one lengthwise wound layer into the next adjacent layer and the separated spaced wire portions are shown in Fig. 1 during their transition from the second into the third layer of the coil; they are denominated by numerals H, l2, it. The coil layer following a completed layer is made by simultaneously winding again a group of five wires around the preceding layer.

Inthismannertheinnerpartoitheeoilwindings is completed.

mirspacerslarenowsetinplaceonthisinner part of the windings and the projecting ends of numbers 3 and spacers 4 are connected by means oi plates I and bolts 0 after insertion of fillers it between the plates and the outer coil windings.

Hereafter the outer part of the windings is completed in the same manner.

The wires may be insulated during the winding procedure or the winding of the coil may be carried out with insulated wires.

Upon completion of the coil the same is insulated and baked. The materials used for the making of the coil supporting structure and for its insulation, such as glass tape, are of inorganic origin exclusively.

When mounting the coil on the core it is advisable to interpose between the latter and the arcuated supporting members I adequately shaped positioning members. I

The novel inductor coil is described and shown as a preferred embodiment of the invention, but it is to be understood that its construction and shape and its manufacture may be varied to suit specific purposes within the sco'pe'indicated by the appended claims; however, it is to be noted that the structural elements of the coil and the materials used for their insulation are made of inorganic materials, such as non-magnetic metals and glass-tape, which increases the usability of the coil for purposes where high operating temperature conditions prevail.

1. In aseli-supporting inductor coil having a substantially rectangular shape and rounded-on corner portions a plurality of adjacent coil windings oi flat copper wire, a cooling duct between the said windings, a first group of arcuated supporting strips extending through the corner portions or said cooling duct beyond the height oi the coil windings, asecond group of arcuated supportingstrips extending in parallel relationsubstantially rectangular shape and rounded-oi! corner portions a plurality of adjacent coil windings of fiat copper wire, a cooling duct between the said windings, a first group of arcuated coil supporting strips extending through the corner portions of said cooling duct beyond the height of the coil windings, a second group of arcuated supporting and spacer strips extending in parallel relationship to said first group adjacent to the inner faces of the corner portions of said coil windings beyond the height of the latter and arcuated spacer plates inserted between and attached to the projecting ends of the first and the second group of supporting strips.

3. In a self-supporting inductor coil having a substantially rectangular shape and rounded-oil corner portions a plurality of adjacent coil windings of flat copper wire, a cooling duct between the said windings, a first group of arcuated coil supporting strips extending through the corner portions of said cooling duct beyond the height of the coil windings, a second group of arcuated supporting and spacer strips extending in parallel relationship to said first group adjacent to the inner faces of the corner portions of said coil windings beyond the height of the latter, arcuated spacer plates inserted between and attached to the projecting ends of the first and the second group of supporting strips and bridging strips connecting the ends of two adjacent supporting strips projecting past the bottom of the coil windings.

MARIO TARA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Madsen Dec. 11, 1945 

